This invention relates to optionally foamed intumescent compositions based on polyurethanes which contain a combination of special polyethers, cyanuric acid derivatives and phosphorus-containing polyhydroxyl compounds as part of their formulation and which are plastic and elastic in character.
Intumescent compositions are understood to be materials which foam under the effect of fire and heat and, in doing so, form an insulating and fire-resistant foam which protects the areas situated behind it against fire. Intumescent compositions such as these are known in the form of lacquers, coatings, mortars and cements.
Good intumescent compositions should be able to at least double their volume on contact with a flame and, in addition, should be unaffected by water. It would be of particular commercial interest if these properties could be combined with the absence of halogen and a low density.
Elastic-plastic intumescent compositions characterized by high dimensional stability could be widely used in the field of fire prevention either in situ or in the form of semi-finished products, such as tape, sheeting, rolls, profiles, coatings, granulates or fillings.
The use of melamine in the production of flexible foams using substantially linear polyols, preferably polyether polyols, is known in principle (German Offenlegungsschrift No. 2,815,554). Although foams of this type are flame-resistant and are not completely consumed on exposure to a flame, they do not have the character of intumescent compositions--they do not undergo any increase in volume forming a fire repellent foam when exposed to a flame.
According to an earlier proposal (German Patent Application No. P 30 25 217.6), flame-resistant sealing compounds free from phosphorus and halogen can be produced using branched polyesters containing hydroxyl groups, but these compounds do not foam when exposed to a flame.
Another earlier proposal (German Patent Application No. P 30 25 309.9) describes optionally foamed intumescent compositions which are obtained by reacting
(a) polyisocyanates with
(b) phosphorus-containing condensation products having at least two hydroxyl groups which are obtained by condensing primary or secondary, aliphatic, cycloaliphatic, aromatic, araliphatic or heterocyclic monoamines and/or polyamines optionally containing OH-groups, carbonyl compounds and dialkyl phosphites, optionally followed by alkoxylation, and
(c) aromatic hydroxy carboxylic acids or their salts and
(d) optionally water and/or other organic compounds containing isocyanate-reactive hydrogen atoms.
According to this proposal, highly branched polyesters containing hydroxyl groups and melamine may also be used.
The products obtained according to this proposal are always rigid.
Still another earlier proposal (German Patent Application No. P 30 41 731.3) relates to optionally foamed intumescent compositions obtained by reacting polyisocyanates with phosphorus-containing condensation products having at least two hydroxyl groups obtainable by condensing primary or secondary aliphatic, cycloaliphatic, aromatic, araliphatic or heterocyclic monoamines and/or polyamines optionally containing OH-groups, carbonyl compounds and dialkyl phosphites, optionally followed by alkoxylation, with polyesters containing hydroxyl groups and having an OH-number of from 140 to 300, obtained by reacting polycarboxylic acids containing from 2 to 10 C-atoms with at least two polyols from two different groups of the following three:
(a) hydroxyl compounds containing more than three OH-groups and having a molecular weight of up to 200, PA1 (b) hydroxyl compounds containing three OH-groups and having a molecular weight of up to 150, PA1 (c) hydroxyl compounds containing two OH-groups and having a molecular weight of up to 80, PA1 R=C.sub.1 -C.sub.8 -alkyl or C.sub.1 -C.sub.8 -hydroxy alkyl and PA1 X=H or methyl. PA1 R=C.sub.1 -C.sub.8 -alkyl or C.sub.1 -C.sub.8 -hydroxylalkyl, preferably ethyl or hydroxy ethyl, and PA1 X=H or methyl, preferably H.
wherein one polyol belongs to group (a) with cyanuric acid and/or cyanuric acid derivatives and optionally water and/or other organic compounds containing isocyanate-reactive hydrogen atoms.
The polyesters recommended are highly viscous so that reaction components characterized by relatively low viscosity are required for processibility.
Although optionally foamed intumescent compositions of this type also show the desirable properties to a satisfactory extent, there is still the fear that the polyesters used could give rise to failure in their longterm behavior when hydrolysis could occur. Because of this, there is a need that the polyester component be potentially completely or partly replaced by hydrolysis-resistant, less viscous and isocyanate-reactive materials characterized by similar service properties to those polyesters.
It has now been found that this is surprisingly possible if special polyethers with functionality greater than two and which are based on ethylene oxide and have an average OH-number of from 150 to 500 are used instead of the polyesters.
In this connection, it was surprising to find that ethylene oxide can only be replaced to a minor extent in molar terms by other alkylene oxides, such as propylene oxide, because otherwise the intumescent compositions obtained would continue to burn vigorously on exposure to a flame and would melt, i.e., would lose their intumescent properties.